To compare pay with prices, divide the pay growth factor by the price growth factor. Subtracting percentages gives only an approximation.
An example with numbers
If pay rises 4% and prices 6%, the real change is 1.04 ÷ 1.06 − 1, around −1.89%. You earn more money and that money buys a little less of the reference basket.
Try it with your numbers
Apply the calculation to two equal periods. Identify the expenses whose price has changed differently from the average.
This calculator is on its way. In the meantime, you can do the calculation on paper or in a spreadsheet.
Example figures for learning purposes. They are not a recommendation and do not replace professional advice.